This is a proposal to closely examine the evolution of microalbuminuria in a unique population-based cohort of 595 individuals enrolled at diagnosis of insulin-dependent diabetes mellitus. This study will evaluate the importance of blood pressure and glomerular hyperfiltration in the development of incipient nephropathy (persistent urinary albumin excretion 20-200mug/mig). Only by studying such a large and unique population prospectively from diabetes diagnosis can be central question about identifying individuals at high risk for development of microalbuminuria be addressed. The singular opportunity here is to compare changes and absolute values of blood pressure and presence of hyperfiltration with development of microalbuminuria yearly in a large group of children and young adults from the time of diabetes diagnosis. The primary goals in following up these individuals are to: 1) determine the relationship between blood pressure and microalbuminuria; and to 2) determine the relationship between glomerular hyperfiltration and microalbuminuria. Longitudinal glycemic control and pubertal stage will be examined in these relationships as possible confounder or effect modifiers. Standardized protocols will be used for yearly measurements of estimated GFR, blood pressure, pubertal status and urinary albumin excretion rate. This study will also take advantage of data and specimens previously collected from this population. The information collected will enable early identification of individuals at high risk for development of microalbuminuria and can lead to recommendations for interventions before the onset of irreversible progression in kidney disease. The uniqueness of this study lies with: careful, comprehensive follow-up of a representative, primarily pediatric population; observation during the time frame in which key factors appear/accelerate; first study of a pediatric cohort that includes non-whites; specimen bank for future testing of new markers (e.g., new DNA assays).